Kristoffer Ajer has joined Premier League newcomers Brentford from Celtic on a five-year deal for an initial £13.5m.

Ajer, who is highly rated and was also a target for Norwich, completed a medical this week and was not in Celtic's squad that drew 1-1 against FC Midtjylland in their Champions League qualifier first-leg on Tuesday.

The fee for Ajer's transfer could rise further with performance-related bonuses.

Brentford head coach Thomas Frank said: "We wanted to get another central defender in, and Kris was our first choice. We think he fits the position-specific profile perfectly, especially on the ball.

"Kris is very composed and can find the right passes between the lines. His level when bringing the ball forward is very high.

"As a defender he has the physicality that you need, and he won his duels when he played in the Scottish league. He can help us in both boxes, with his strength in the air.

"He is a player at a good age, and we think he come straight in and be ready to perform in the Premier League. But he also fits the way we want to recruit players and work with them.

"He can develop as a player and both Brentford FC and Kris can move to a higher level in the coming years."

Ajer had been with Celtic since 2016 and after a loan spell at Kilmarnock in 2016/17, signed a new four-year deal with the Hoops in 2018.